1. Field of the Invention
The present invention relates to an image forming apparatus and an image scanner such as a printer, a facsimile machine or a copying machine, and particularly relates to a structure of image forming apparatus in which a recording head unit including nozzle arrays each having a plurality of nozzles for ejecting ink onto a recording medium is attached to a carriage.
2. Description of the Related Art
Some image forming apparatus in the background art such as printing machines, facsimile machines and copying machines are of an inkjet system in which ink droplets are ejected from nozzles of an inkjet head so as to form an image on paper as a recording medium. For example, of such apparatus, some are of a type in which are cording head unit having one or more nozzle arrays each comprised of a plurality of nozzles is attached to a carriage provided movably forward and backward in a direction crossing a conveyance direction of a recoding medium so that the nozzle arrays extend long in the conveyance direction, but some are of a type in which a recording head unit having one or more nozzle arrays each comprised of a plurality of nozzles is attached to a fixed carriage so that the nozzle arrays extend in a direction crossing a conveyance direction of a recoding medium. In either type, the printing quality is greatly affected when the array direction of the nozzle arrays in the recording head unit is correctly aligned with the conveyance direction of the recording medium. It is therefore extremely important to align the recording head unit correctly with the carriage to which the recording head is attached.
As such a technique for aligning a recording head unit with a carriage, a document JP-A-2003-053947 discloses an inclination adjusting mechanism for adjusting the left/right inclination of the recording head unit. According to the document, an eccentric rotor (cam) is attached to the lower portion of the right side surface of the carriage, while an abutment portion (pad block) is provided in the lower portion of the right side surface of the recording head unit so as to project outward. The abutment portion is disposed so that the eccentric rotor abuts against the back surface of the abutment portion. The recording head unit is thus received in the carriage. In this configuration, the abutment portion is moved by the rotation of the eccentric rotor so that the recording head unit is rotated and moved relatively to the carriage. Thus, the array direction of the nozzle arrays in the recording head unit is adjusted to be in position with respect to the carriage, and hence the inclination with respect to the conveyance direction of the recording medium (or a direction crossing the conveyance direction) is eliminated.
On the other hand, in the configuration according to the document JP-A-2003-053947, pressed portions are made to project outward from the upper portions of the left and right side surfaces of the recording head unit respectively. The pressed portions are locked in recess portions of the left and right side surfaces of the carriage respectively. The pressed portions are pressed obliquely downward by wire springs attached to the left and right side surfaces of the carriage respectively. Thus, a force to press the recording head unit onto the back surface and the bottom surface of the carriage simultaneously is generated so that the recording head unit removably attached to the carriage is prevented from rattling or being out of position.